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Thu, 01 Oct 2026 06:43:45 -0700 (PDT) Received: from gourry-fedora-PF4VCD3F ([2620:10d:c092:500::6:7dd1]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4a023ecef86sm33062845e9.3.2026.10.01.06.43.43 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 01 Oct 2026 06:43:44 -0700 (PDT) Date: Thu, 1 Oct 2026 09:43:42 -0400 From: Gregory Price To: Ackerley Tng Cc: Hugh Dickins , Baolin Wang , Andrew Morton , Sean Christopherson , Paolo Bonzini , David Hildenbrand , Jonathan Corbet , Shuah Khan , Randy Dunlap , Shuah Khan , vannapurve@google.com, erdemaktas@google.com, jxgao@google.com, rientjes@google.com, fvdl@google.com, jthoughton@google.com, tarunsahu@google.com, pratyush@kernel.org, fuad.tabba@linux.dev, David Woodhouse , yan.y.zhao@intel.com, michael.roth@amd.com, suzuki.poulose@arm.com, Christian Brauner , Jason Gunthorpe , Nicolin Chen , Xu Yilun , aik@amd.com, aneesh.kumar@kernel.org, Vlastimil Babka , kernel-team@android.com, kernel-team@meta.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, kvm@vger.kernel.org, linux-doc@vger.kernel.org, linux-kselftest@vger.kernel.org Subject: Re: [PATCH RFC 00/17] Allow guest_memfd to be created using a resource (pool) fd Message-ID: References: <20260925-gmem-tmpfs-backend-v1-0-d36159822d18@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260925-gmem-tmpfs-backend-v1-0-d36159822d18@google.com> X-Rspam-User: X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: 820684000A X-Stat-Signature: sobykeq4hm5g3qktaoepm13sdm7p6cy5 X-HE-Tag: 1790862226-564553 X-HE-Meta: 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 GnhECXcr /woUNDl0L466mqap+Sk6On/8u9s+x5uwq1pGZENbujvXhv4lpm5UX7l6t7LrQPSELsLwbbitfSVHpojToYBoL6p3smfna/pXX7Vnm4w1AAwEIaeV1RaB3/q8cSAhoxrZHn/csgTIFCgVNeCv1aRucOTZomCLMthXvyXMEISKFo4m7i70GGflH7C0CiCs7wLbcOiQ7ng0hAg+XDr49lgULD94mvwJMRIrkwVzc4tGaDBPFeSK1iayJBkuQ5fVAv/+sMbBcSCOB8j2LoY11Hz56IH6+tS0uZlNf9v0U9OmzSJSCbJ+MQrElkBliPbLtiOU+06XfyyPwZMOg2uuActU+L6AdFkxhUAsGLW4jHRfg5YExthocE5lglIaauL0Hu7G15RoLrmpEptyDAKPaQWllgzWkjQ8kjREiPmh+ Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Fri, Sep 25, 2026 at 05:50:47PM -0700, Ackerley Tng wrote: > + e.g. for tmpfs, > + Use mount page size. > + Respect mount size limits. > + Use guest_memfd mpol and fall back to mount mpol. > + Gregory, now you can set mpol upfront on a mount! [3]) I haven't had time to quite give this the read it deserves yet (have been traveling this past week), but I think this mpol/mount issue can be solved with a new dax driver (which maybe provides this provider interface) without needing to involve numa policy at all. Essentially fd = open("/dev/cxl_dev", ...); /* backed by anondax driver */ then later when a fault on that fd happens, the driver provides an anon-memory allocation that explicitly requests the node associated with that device - as opposed to trying to jam this into mempolicy. If you're planning to be at LPC, happy to discuss this in person, but I think this provider pattern is likely much cleaner without mempolicy at all if you can just make the provider do that allocation path for you. ~Gregory